Abstract: A system for initiating the operation of an electronically-operated device is disclosed. The system comprises a key unit having a code pattern mounted on a circle around the center thereof, a first rotating sensor eccentrically mounted with respect to the center of the key unit and adapted to scan the code pattern on the key unit and generate a first output signal which is representative of the code appearing on the key unit, a second sensor adapted to detect the rotational speed of the first rotating sensor and to generate a second output signal which is representative of the rotational speed of the first rotating sensor, a signal-processing circuit responsive to the first and the second output signals for generating a control signal which is independent of the rotational speed of the rotating sensor, and an electrically-operated device responsive to the control signal to perform a given function when a valid code is generated.